This application relates to a counterweight for use in a variable pitch propeller blade assembly.
Propeller rotors typically include a plurality of blades having airfoils. The rotor is provided with a pitch change mechanism that may be hydraulically powered. The pitch change mechanism changes an angle of incidence of the airfoils.
At times, the hydraulic power for changing the pitch of the airfoil has failed. In such a case, it is desirable to increase the pitch angle, rather than allow forces on the unpowered blade to drive the blade airfoil toward a decreased pitch angle.
To this end, counterweights have been fixed to the blade in the past with the counterweight designed to be attached to a base of the blade and produce a twisting moment on the blade when the propeller rotor rotates, such that in that moment on the blade is in a direction to increase pitch.
To optimize the design of the counterweight, it is desirable to place the counterweight at a largest radius from a blade pitch change axis as allowable. However, the blade pitch angle must be capable of movement from a full reverse position to a feather position. The feather position is essentially the position at which the blade is parallel to an approaching air flow.
To achieve the transition between the reverse and feather positions, the counterweight must be capable of passing the adjacent blades. This limits the radius that may be utilized between the counterweight and the blade rotational axis.